The prior art includes a number of procedures for depositing thin films of metals and refractory metals on both conductive and nonconductive substrates. For deposition of diamond-like carbon coatings, chemical vapor deposition and vapor phase deposition techniques are predominant. Chemical vapor deposition procedures include hot filament emission systems, plasma assisted deposition systems, plasma jet and DC arc jet systems. Each of the deposition-procedures requires that the substrate have a high temperature. The processes further employ a gas mixture with a large percentage of hydrogen. High concentrations of hydrogen often result in polymer-like hydrocarbon impurities in the films and require an addition of gases like oxygen to burn off the polymer. Vapor phase deposition procedures include carbon arc systems, sputtering and laser ablation systems. While such systems maintain the temperature of the substrate relatively low, substantial effort is required to control the properties of deposited films. Further, scale-up of vapor phase deposition processes to enable continuous deposition, requires substantial investment.
Ion beam deposition systems have become more widely used. Most such systems employ a plasma or gas discharge to generate the ion beam. Other systems bombard a target with a first ion beam to cause the production of an opposite charge second ion beam, whose ions are then deposited on a substrate. It has been determined that the use of cesium ions as the bombarding first ion source produces a high yield of opposite charge ions from metal and refractory metal targets. Solid state cesium sources have been developed for ion beam deposition systems. Kim and Seidl describe a solid source of Cs.sup.+ ions in "Cesium Ion Transport Across A Solid Electrolyte-Porous Tungsten Interface", Journal of Vacuum Science Technology A7(3), May/June 1989, pages 1806-1809, and "A New Solid State Cesium Ion Source", General Applied Physics 67(6), 15 Mar. 1990, pages 2704-2710. The Cs.sup.+ - source solid electrolyte comprises a cesium-mordenite solid electrode which is sandwiched between a porous tungsten emitting electrode and a nonporous platinum electrode. A combination of an applied voltage and heat enables Cs.sup.+ ions to be emitted. Further details of the solid electrolyte cesium source can be found in "The Theory of Metal-Solid Electrolyte Interface", Materials Research Society Symposium Proceedings, vol. 135, pages 95-100 and in U.S. Pat. No. 4,783,595.
The Kim et al. cesium ion source, in ion gun form, has been used for ion beam sputter deposition of gold, copper, molybdenum, tungsten and tantalum. The cesium particles from the solid-state cesium ion gun pass through a pair of deflecting plates which cause the cesium ion beam to be directed towards a target that lies to one side of the center line of the ion gun and not in its direct path. A substrate positioned opposite the target, and on the other side of the center line of the ion gun, receives the sputtered molecules that are liberated from the target as a result of the cesium bombardment. (See "Solid-State Cesium Ion Gun for Ion Beam Sputter Deposition" Kim et al., Review of Scientific Instruments, vol. 63 (no.12), December 1992, pages 5671-5673.)
Pargellis et al. in "Sputtering Negative Carbon Ions From Cesiated Graphite Surfaces" Journal of Vacuum Science Technology A1(3), July/September 1983, pages 1388-1393, describe a system for sputtering of negative carbon ions from graphite targets that are bombarded with cesium ions. Pargellis et al. bombarded a graphite block from a source of cesium atoms piped into the ion beam generation region from a cesium oven. The bombardment of the graphite target by the positive cesium ions causes generation of negative carbon ions. Few details are given regarding the specific arrangement of the cesium ovens and the various ion beam extraction electrodes.
Ion beam deposition has many benefits when compared with chemical vapor deposition. Ion beam deposition procedures enable room temperature deposition. The deposition rate of metal negative ions is not effected by temperature. Little or no sample surface preparation is required and the procedure employs no hydrogen in the ion beam atmosphere. The deposition rate from a focused negative ion beam can be as great as 100 microns per hour. In general, vapor phase prior art deposition procedures have not enabled metal ions to be deposited over large deposition areas.